It is required that a DC power supply used for a plasma generator should control excess current when an arc is generated, and extinguish the arc at a high speed. A voltage-type DC power supply has problems, including that a large capacitor connected to an output may cause an excess discharge current to pass, when an arc is generated, and in order to compensate for a drop of output voltage upon arc occurrence, the output is made to increase more, and this may result in an impact on the load, such as extension of the arcing time.
Some methods as the following are known for addressing arc discharge:
1) The power supply is suspended, and the operation is restarted after a lapse of a certain period of time;
2) An LC oscillation circuit made up of a combination of a reactance and a capacitor generates reverse voltage, thereby causing arc self-extinguishing; and
3) An reverse voltage generation circuit including a solid-state switching element generates reverse voltage, thereby causing arc self-extinguishing.
In the methods as described above, there are already found some problems, including a point that if the arc discharge frequently occurs, the output current may become uncontrollable, and a point that a temporal delay may occur for restarting normal discharge, and the like.
In order to solve the problems described above, a DC power supply for plasma is suggested to control the amount of power to be supplied to a plasma generator, by employing a current source inverter as an inverter and controlling a switching operation of the current source inverter as a current source (Patent Document 1).